Quantum confinement in nanoscale silicon: The correlation of size with bandgap and luminescence

• Published in: Solid state communications 1998-02, Vol.105 (5), p.317-322
• Main Authors: von Behren, J., van Buuren, T., Zacharias, M., Chimowitz, E.H., Fauchet, P.M.
• Format: Article
• Language: English
• Subjects: A. nanostructures; Condensed matter: electronic structure, electrical, magnetic, and optical properties; E. light absorption and reflection; E. luminescence; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in multilayers, nanoscale materials and structures; Exact sciences and technology; Fullerenes and related materials; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Physics; Small particles
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/S0038-1098(97)10099-0

The optical properties of silicon nanocrystallites of known sizes, present in supercritically dried porous silicon films of porosities as high as 92%, have been measured by a variety of techniques. The bandgap and luminescence energies have been measured as a function of size for the first time. The bandgap increases by more than 1 eV due to quantum confinement. The peak luminescence energy which also shifts to the blue is increasingly Stokes shifted with respect to the bandgap, as the size decreases. The measured bandgap is in agreement with realistic theories and the Stokes-shift between bandgap and luminescence energies coincides with the exciton binding energy predicted by these theories. These results demonstrate unambiguously and quantitatively the role of quantum confinement in the optical properties of this indirect gap semiconductor.